In Wikipedia [1] the following definition of a Special Ordered Set of Type 1 (SOS1) is given:
This is not completely correct. A SOS1 member can be a negative variable or a free variable. Such a variable may take a negative value.
An example:
The results are:
Indeed, we see a single negative value.
Special Ordered Sets of type 1 (SOS1 or S1): are a set of variables, at most one of which can take a strictly positive value, all others being at 0.
This is not completely correct. A SOS1 member can be a negative variable or a free variable. Such a variable may take a negative value.
An example:
 |
| Model with SOS1 variables with a negative lower bound |
The results are:
---- VAR x
LOWER LEVEL UPPER MARGINAL
i1 -1.0000 . +INF 1.0000
i2 -2.0000 . +INF 1.0000
i3 -3.0000-3.0000 +INF 1.0000
LOWER LEVEL UPPER MARGINAL
---- VAR z -INF -3.0000 +INF .
Indeed, we see a single negative value.
References
- Special Ordered Set, https://en.wikipedia.org/wiki/Special_ordered_set